1. Technical Field
The present invention relates to a pedal apparatus having hysteresis, and more particularly, to a pedal apparatus having a hysteresis structure reduces noise generated when an accelerator pedal is operated by reducing a radius of rotation of a friction member.
2. Related Art
Generally, an accelerator pedal installed in a vehicle is designed to accelerate the vehicle by adjusting the amount of air sucked in by an engine or the amount of fuel injected into the engine according to an angle at which the pedal is rotated by a force applied when a driver presses the pedal. When the driver presses or releases the accelerator pedal, a different amount of “pedal effort” is generated according to the degree to which the driver depresses the accelerator pedal. Pedal effort is the amount of force applied by a driver on a pedal at any instance in time. Then, the pedal effort is delivered to the engine via a line or a cable, thereby adjusting the speed of the vehicle. Alternatively, the pedal effort causes a sensor level coupled to the pedal to rotate when the pedal rotates, and an output value of the sensor lever is transmitted to an engine controller, which then electronically adjusts the speed of the vehicle. According to the installation position, accelerator pedals are classified into pendant-type pedals hanging from a dash panel or organ-type pedals installed on a floor panel.
An accelerator pedal is generally equipped with a hysteresis generating apparatus. The hysteresis generating apparatus can significantly reduce a driver's fatigue by controlling the pedal effort generated when the driver presses the pedal and a force applied to the driver's foot by the pedal when the driver releases the pedal to be different from each other.
FIG. 1 is a graph illustrating a hysteresis effect brought about by a frictional force generated in an accelerator pedal. Referring to FIG. 1, a line 1a represents an angle of rotation (or stroke) of the accelerator pedal with respect to the force acting between a driver's foot and the accelerator pedal when no friction is present.
In a hysteresis structure, when the pedal rotates, a frictional force is generated in a direction that hinders the motion of the pedal. Therefore, when the driver presses the pedal, not only a force that rotates the pedal but also a force that is larger than the frictional force are required as represented by a line 1b. Therefore, significant amount of pedal effort is required. On the other hand, when the driver releases the pedal, the frictional force offsets a force (e.g., an elastic force of a spring) that returns the pedal to its original position. Therefore, as represented by a line 1c, the force applied to the driver's foot by the pedal is reduced compared with when the frictional force is not acting. As a result, the driver feels far less fatigue when operating the accelerator pedal.
For a driver's convenience, a hysteresis generating apparatus is essentially installed in an accelerator pedal apparatus. The hysteresis generating apparatus generally includes a friction part which operates in accordance with the rotation of the pedal to produce friction. To apply the friction part, a conventional hysteresis generating apparatus is structured to use many parts. Therefore, the conventional hysteresis generating apparatus has a complicated structure. Due to the complicated structure, the conventional hysteresis generating apparatus is highly likely to break down. In addition, since a trajectory along which the friction part moves to generate a frictional force is quite significant, noise is created when the accelerator pedal apparatus operates. Furthermore, the accelerator pedal apparatus takes up a large amount of space.